Neuronal unit activity in the abducens nucleus during classical conditioning of the nictitating membrane response in the rabbit (Oryctolagus cuniculus).

Abstract

Neuronal unit activity was recorded from the abducens (6th nerve) nucleus, the "final common path," during classical conditioning of the nictitating membrane (NM) response in the rabbit, with the use of a tone conditioned stimulus, an air puff unconditioned stimulus (UCS), 250-msec interstimulus interval, and 60-sec intertrial interval. Animals were given 2 days of conditioning training (104 trials in eight blocks per day) and 1 day of extinction. Control animals were given comparable periods of stimulus presentations, explicitly unpaired. Activity of small clusters of units-"multiple unit" recording-was compared with the amplitude-time course of the NM response. Between-blocks comparisons of neural and behavioral responses indicated an essentially perfect correlation during acquisition of the conditioned response (Day 1, r = .99; Day 2, r = .98) and a slightly lower correlation during extinction (r = .93) for the conditioning animals. Within-blocks comparisons indicated a close correspondence between the histograms of unit activity and the amplitude-time course of the NM response for the conditioning animals in all phase of training and for the control animals in the UCS trial blocks. *Analysis of the neural mechanisms of of processing, it is necessary to compare learning and memory has proved extraordi-putative learning-related changes in other narily difficult. The goal is localization and brain structures with the temporal course of analyses of the alterations in neuronal ac-altered activity in motoneurons. tivity that code learning-the "engram"We have adopted classical conditioning of

Effects of ipsilateral rostral pontine reticular lesions on retention of classically conditioned nictitating membrane and eyelid responses

“…In mapping, we typically record multiple-unit activity, but isol~ted single-unit recording can also be done using higher impedance microelectrodes. Vnit discharges are converted to standard pulses and stored and analyzed in a computer, as described previously (Berger & Thompson, 1978;Cegavske, Patterson. & Thompson, 1979).…”

Accessory abducens nucleus and conditioned eye retraction/nictitating membrane extension in rabbit

“…First, Lorente de No reported more than 50 years ago, in quite a different context, that cornea1 stimulation caused activation of the retractor bulbi as well as the other six extraocular muscles in rabbit. Cegavske et al (1976Cegavske et al ( , 1979 had reported that abducens multiple units were highly correlated with conditioned and unconditioned NM extension in the rabbit. Later, Harrison et al (1976) reported the same phenomenon for oculomotor nucleus multiple units.…”

Neural Substrates of Eyeblink Conditioning: Acquisition and Retention

“…Initial studies of motor control of the reflex and conditioned responses focused on NM extension, actually eyeball retraction, controlled mostly (but not entirely) by the retractor bulbus muscle, innervated largely by axons of the sixth nerve originating in the accessory abducens (and to a much lesser extent, abducens) nuclei. However, the other extraocular muscles also contract synergistically with the retractor bulbus or relax in an antagonistic manner in the case of the levator palpebrae motor neurons (Cegavske et al 1976(Cegavske et al , 1979(Cegavske et al , 1987Berthier et al 1987;Disterhoft et al 1987). At the time there was much debate about the details of innervation of the retractor bulbus muscle, which in retrospect was somewhat irrelevant because the most prominent and sensitive component of the response is EMG activity in the orbicularis oculi muscle controlling external eyelid closure ), innervated by the seventh nerve from the facial nucleus.…”